Chair base having porous air discharge unit and method of making the same

ABSTRACT

1,174,490. Air cushion supported chairs. DENTISTS&#39; SUPPLY CO. OF NEW YORK. 24 Oct., 1967 [22 Dec., 1966], No. 48367/67. Heading B7K. Apparatus for supporting a chair, in the embodiment a dentist&#39;s chair, for easy movement, comprises a pillar 66 to which the seat (not shown) is attached mounted on a baseplate 20 to which are attached three air cushion pads 22, each comprising a plate 24 shaped to form a cavity 32 and having a flexible porous sheet 42 secured around its periphery, and a resilient ring 52 to form a support pad when in contact with the floor 12. The sheet 42 is clamped by means 54, 56, 58 to the centre of base 20 through the medium of an apertured plate 36 and plates 20 and 24 are formed with central apertures whereby air may be delivered from a blower 80 through flexible hoses 84 to the cavity 32 to inflate porous sheet 42 so that air passing therethrough will form an air cushion 60 to support the base and the seat.

Mam}! 18, 1959 R. A. BRESNAHAN 33,320

CHAIR BASE HAVING POROUS AIR DISCHARGE UNIT AND METHOD OF MAKING THE SAME Filed Dec. 22, 1966 Sheet 1 of 5 ROBERT A. BRESNAHAN ATTORNEY March 18. 1969 R. A. BRESNAHAN 3,433,320

CHAIR BASE HAVING POROUS AIR DISCHARGE UNIT AND METHOD OF MAKING THE SAME Filed Dec. 22, 1966 Sheet 3 of 5 ATTORNEY March 1969 R. A. BRESNAHAN 3,433,320

CHAIR BASE HAVING POROUS AIR DISCHARGE UNIT AND METHOD OF MAKING THE SAME Filed Dec. 22, 1966 Sheet .3 off:

FIG.6

mvgmon ROBERT A. BRESNAHAN AI'IORNEY United States Patent ()ffice 5 Claims Int. Cl. B60v 1/00 ABSTRACT OF THE DISCLOSURE A self-leveling mobile supporting base for a chair seat of the type normally employed in the dental profession, barber shops, and beauty salons for purposes of moving the chair and person seated thereon along the floor, or elevating the chair and occupant to the most comfortable and efiicient location for the operator and occupant.

Cross-reference to related application The invention embodies a different principle from that described in copending application Ser. No. 470,984, filed July 12, 1965, now Patent No. 3,347,330; in the name of William R. Heathe and assigned to the assignee of the present invention, for effecting the self-leveling of a supporting base for a chair seat of the type referred to above.

Background of invention For many years, it has been customary in chairs used by dentists, barbers and beauty operators to utilize adjustable means by which the seat could be elevated relative to a stationary base and/or rotated about a fixed vertical axis. The basic concept of making a chair of this type movable horizontally over a supporting floor surface or the like by generating an air film beneath the base upon which the same glides over a supporting surface is disclosed in copending application Ser. No. 275,- 594, now Patent No. 3,295,621, in the names of H. U. Deeley, Jr., et al., and assigned to the same assignee as the present invention. Such a chair has a single base member which generates and is supported upon such an air film when horizontal linear movement or rotatable movement about a vertical axis is desired. If a chair of this type is loaded eccentrically, such as by attaching additional apparatus thereto, or the like, for example, such desired movement of the chair is rendered difficult. Such difficulty is largely overcome by the structure of said aforementioned Patent No. 3,347,330.

Summary of the invention Although said aforementioned Patent No. 3,347,330 will overcome the aforementioned difiiculty of movement when a chair is eccentrically loaded, the mechanism in said disclosure by which reasonably satisfactory self-leveling of a chair is achieved is relatively complex. In contrast thereto, the present invention achieves at least equal, if not superior, self-leveling of a chair of the type described by employing means to restrict peripheral discharge of air from the perimeters of the porous, flexible air discharge members extending across the bottoms of a plurality of spaced but closely related air-cushion pad units and thereby provide for the formation of a greater area of a supporting film of air beneath any one or more of the pad units which are more heavily loaded than the other units, whereby there is provided cooperating and automatically proportioned supporting air-films beneath spaced portions of said chair base to insure ready horizontal or rotatable movement thereof relative to a supporting surface such as a floor. In addition, the dischargerestricting means eliminates flutter which tends to develop 3,433,320 Patented Mar. 18, 1969 in said porous air-discharge members when the characteristic features of the present invention are not utilized.

Description of the drawings FIG. 1 is a side elevation of a chair base embodying the principles of the present invention and illustrating an exemplary chair seat, shown in phantom, attached to the chair base for mobile support thereby with respect to an exemplary floor surface.

FIG. 2 is an enlarged top plan view of the chair base per se of the type illustrated in FIG. 1.

FIG. 3 is a side elevation of the bottom portion and operating mechanism of the chair base shown in FIG. 2 after the cover has been removed.

FIG. 4 is a top plan view of the portion of the chair base shown in FIG. 3 as seen on the line 4-4 of said figure.

FIG. 5 is a fragmentary vertical sectional view, partly broken away to foreshorten the same transversely, showing a portion of one of the air-discharge members of the plurality thereof included in the chair base shown in the preceding figures, said view showing the air-discharge member in the exemplary position which it assumes when sustaining minimum loads as when the chair seat is unoccupied.

FIG. 6 is a fragmentary view similar to FIG. 5, but showing the exemplary position of the discharge member with respect to the 'base when sustaining substantially maximum load.

FIG. 7 is a fragmentary view similar to FIGS. 5 and 6, but showing the relative positions of the air-discharge means when the base is at rest.

Description of the preferred embodiments It is to be understood that the chair base comprising the present invention is intended to be used to support chair seat and/or chair back arrangements of various kinds for use in professions or businesses in which it is desired to move the occupant of the chair with comfort and for efficiency in regard to performing various services upon the occupant by an operator. Accordingly, the chair base of the invention is adapted for use with appropriate chair seats and/ or backs to be used in dentistry, barber shops, beauty salons, and other similar types of professions and businesses, without being restricted to those specifically enumerated.

For a long period of time, it has been customary for dental chairs, barber chairs, and the like, to be mounted stationarily at least with respect to a fixed vertical axis, upon a floor surface, whereby it has been necessary either for the dentist, dental assistant, barber, or the like, to carry certain equipment, preparations, or accessories to the occupant of the chair or the chair occupant has to leave the chair and walk to another location. Particularly in the dental profession, however, it now has been found to be substantially more efiicient, as well as more comfortable to both the patient and the operator, such as a dentist or dental assistant, to be able to move the patient to different locations, while remaining seated or reclining in a mobile type of chair. Hence, it is preferred in accord ance with this invention that the chair not only may be moved vertically as is now common practice, but that it may also be moved pivotally about a verticaly axis and particularly that it may be moved horizontally with respect to the supporting floor surface.

By rendering the chair mobile, therefore, in the manner referred to above, it is possible to arrange the equipment in a dental oflice, beauty salon, barber shop, or the like, more efficiently than at present where it is necessary to have the same capable of being moved to the occupant of the chair rather than vice versa. For example, in a dental office, cavity preparation and filling equipment may be efiiciently and compactly arranged at one location in the operatory, X-ray equipment at another location, crown and bridge equipment and material at another location, and denture preparation equipment and material, such as impression-forming substances and holders, at still another location, to mention only some of the more salient types of equipment and materials used in a normal dental operatory. To be able to move the patient to these locations in the operatory not only affords efiiciency and comfort to the patient and operator, such as the dentist or dental assistant, but, in addition, such an arrangement readily makes it possible for a dentist to work upon a patient from whichever side is more convenient and regardless of whether the dentist is inherently left-handed or right-handed.

As has been indicated in said Patent No. 3,347,330, particularly when additional equipment is to be supported by the chair or chair base, such as a light which preferably extends from one side of the combination base and chair of the type referred to above, by means of a bracket connected to the upper end of the base, but not shown in the drawings, and employing a post extending vertically from the outer end of the bracket arm to support a suitable dental light at the upper end of the post, it can be appreciated that the chair base will be loaded eccentrically due to the weight of the light and bracket alone. There also may be additional equipment supported either by the chair seat, chair arm, or chair base, such as trays, control units, and cuspidors, all of which will tend to induce eccentric loading of the base of the chair. Further, there sometimes is a tendency for a patient to sit in the chair closer to one side than the other, thus resulting in eccentric loading of the base, especially if the patient is heavier than average.

When such eccentric loading of the base occurs, if it is desired to move the base upon the intended film of air which renders the base mobile with respect to the floor surface, it has been found that the side of the base which is the most heavily loaded tends to engage the floor surface with sufficient friction that it sometimes is quite difficult to move the base over the floor surface as desired. The base, as it were, tends to dig into the floor surface at the low side. To obviate this situation, the structure comprising the subject matter of the copending application resorts to valve arrangements which attempt to discharge a greater volume of air from the discharge unit or member adjacent the lower side of the base, while attempting to restrict the volume of air delivered to the discharge members on the so-called high side of the base, thus affording greater sustaining effect to the discharge member at the low side of the base.

In contrast to the foregoing, it has been found that a satisfactory self-leveling of the chair base may be provided when the base is eccentrically loaded and tends to tilt more to one side than the other by controlling the area of the flexible, air-discharge members extending across the bottom of the chair base in circumferentially spaced arrangement around the central axis of the base, in conjunction with restricting the discharge of air from the porous discharge member, such as by preventing the discharge of air from the peripheral portions of each of the flexible discharge members, details of which are set forth hereinafter.

Referring to the drawings, and particularly FIG. 1, it will be seen that the chair base is disposed upon a suitable, preferably flat supporting surface such as a floor 12. Mounted operably upon the upper end of the base 10 is an exemplary chair seat 14. For purposes of simplifying the present illustration, the chair seat specifically illustrated comprises the seat of a dental chair to which a back 16 is pivotally connected and an arm 18 also is movably mounted operatively with respect to the seat 14 and back 16. Such seat is intended to be representative of the various types of chairs to which the invention pertains, as described above.

The means by which the seat 14 is connected to the upper end of the base 10 does not comprise part of the present invention and, therefore, details of the same are not shown. However, it is to be understood that the seat 14 and especially the back 16 can be tilted either individually or simultaneously about a horizontal axis with respect to the base 10 and also raised and lowered along a vertical axis with respect to said base.

The present invention primarily is concerned with the mechanism by which air is discharged under pressure from the bottom surface of the base 10 for purposes of creating an air film between said bottom surface and the supporting surface 12 for purposes of permitting the chair base and all items supported thereby to glide upon said film of air with a minimum of effort being expanded by the operator, such as a dentist, for purposes of moving the occupant of a chair from one position to another, regardless of whether such movement occurs in a horizontal direction or rotatably about a horizontal axis, or a combination of the same and regardless of whether the base is eccentrically loaded, at least to a reasonable extent, or not. Details of such mechanism for generating or creating said air film will now be described.

The chair base 10 essentially comprises a base plate 20 which, as shown in FIG. 4 in particularly, preferably is triangular in shape. Connected to the base plate 20 adjacent the corners thereof is a plurality of pad-like air discharge units 22 which are, basically, similar in construction. As a result of the arrangement shown in FIG. 4, it will be seen that the air-discharge units or means 22 are spaced substantially evenly around what can be considered an imaginary circumference of the base plate 20 and especially with respect to the perpendicular central axis thereof. The air-discharge units 22, therefore, may be considered to be substantially evenly spaced circumferentially about said axis.

Referring to FIGS. 5 and 6, it will be seen that the principal elements or components of each of the pad-like air-discharge units 22 comprise a mounting plate 24 which preferably is circular in plan view. Each of these mounting plates is provided with a central opening 26 which preferably is of similar size and shape to complementary, similar discharge openings 28 that respectively are formed adjacent the corners of the base plate 20. The openings 26 and 28, therefore, are preferably coaxial, as can be seen from FIGS. 5 and 6. The units 22 also are readily detachably connected to the corner portions of base plate 20 by means of a plurality of bolts 30 which extend through suitable openings in the base plate 20, for example, and are received in tapped holes formed in the mounting plates 24. Preferably, the heads of the bolts 30 are adjacent the normally upper surface of the base plate 20 for ready access and manipulation thereof.

The mounting plates 24 are of a substantially uniform thickness and preferably are fiat throughout at least the major portion of the area thereof, except adjacent the periphery, where, as will be seen from FIGS. 5 and 6 in particular, said peripheral portion is curved evenly downwardly a limited distance so as to define a shallow circular space 32 immediately below the inner surface of the mounting plate 24. Said space comprises a relatively thin plenum chamber, for purposes to be described in greater detail hereinafter. The lower surface of each of the m o unting plates 24 also is formed with an annular undercut 34 which is complementary to and receives a central mounting disc 36 which is secured within the annular undercut 34 by appropriate screws 38. A plurality of air-discharge ports 40 also are formed in discs 36 in spaced relation to the central axis and each other.

A fiexible, porous or permeable air-discharge member 42 extends across the bottom of the mounting plate 24 of each pad-like air-discharge unit 22. The members 42 are cut from appropriate sheet material, either of a woven or non-woven nature and comprising a multitude of tiny,

adjacent pores or openings such as are present in woven cloth, for example, and thereby render the member 42 permeable especially to a fluid such as air. A porous woven cloth formed from so-called plastic or synthetic resinous filaments or fibers is highly suitable for the purpose. Especially in view of the fact that the flexible member 42 directly and slidably engages a supporting surface such as the floor 12, forming the same from synthetic resinous material which, due to the relative hardness and tendency to be self-lubricating, has been found to substantially prolong the life thereof.

Without restriction thereto, one specific type of flexible, porous material from which the member 42 may be formed and has proven satisfactory comprises a woven fabric having the following characteristics:

A twill-like woven fabric formed from poly-propylene filaments spun into a yarn or thread to provide a count of about 57 threads to the inch in one direction and 36 threads to the inch in the other direction provides interstices or pores between the woven yarn or threads which will retain particles as small as 75 microns in diameter but will pass particles of smaller size.

It also is to be understood that suitable and effective flexible porous material from which the members 42 may be formed conceivably can comprise sheet material which initially is impervious and a multitude of small holes may be formed therein by piercing or puncturing, such as by mechanical means, or chemical etching. In the event the sheet material is formed from synthetic resinous material, particularly of a thermoplastic nature, any mechanical perforating members which are used may be heated to facilitate the penetration and also induce stability in the holes thus formed. However, the woven type of porous material is preferred for added reasons described in detail hereinafter.

Discs of such flexible, porous material as referred to above may be stamped or cut so as initially to have a radius several inches greater than that of the radius of the mounting plate 24 to which it is to be attached. The excess material at the circumference comprises a binding or mounting flange 44 which is extended upwardly, somewhat perpendicularly from the frame of the main portion of the member 42, as shown in FIGS. 5 and 6, and thereby overlying the peripheral wall of the mounting plate 24. In the preferred construction, an annular, vertical recess 46 is formed in said peripheral wall, as shown also in FIGS. 5 and 6, for purposes of receiving the terminal edge portion of the binding flange 44. Attachment of the flange 44 to the mounting plate 24 is completed by means of a clamping band 48 of any suitable nature, such as a metal strap provided with a suitable tensioning means, or the like, not shown in detail in the drawings.

The lower peripheral surfaces of the mounting plates 24 also are provided with a horizontally extending, somewhat shallow annular recess 50. Mounted within said recess and extending a limited distance below the same is an annular compressible ring 52. which is formed from rubber-like material for purposes of forming a cushiontype of contact surface against which the peripheral portion of the flexible porous member 42 abuts when the chair base is at rest upon the supporting surface 12, for example. By such arrangement, under normal conditions of operation, no part of the mounting plate 24 contacts the inner surface of the flexible, porous member 42 when said base is at rest as described. Accordingly, no undue harm is sustained by the member 42 under such circumstances.

In the preferred arrangement of the construction comprising the present invention, the central portions of each of the flexible, porous members 42 are fixedly attached to the mounting plate 24, such attachment specifically being made to the lower surface of the central mounting disc 36 carried by each of said plates 24. As best shown in FIGS. 5 and 6, a pair of appropriate, preferably metallic reinforcing members, such as washer-like discs 54, of

any suitable material, are applied respectively to opposite surfaces of the center of the member 42 and a clamping disc 56, formed of sheet metal, stiff fiber, or the like, is secured against the outermost reinforcing member 54 by means of a clamping bolt or screw 58 which extends through a suitable hole in the center of the mounting disc 36 of each unit 22.

By the arrangement just described, it will be seen that the effective, flexible, lowermost, operating portion of the porous members 42 is somewhat annular, due to the fact that the central portion of each member 42, which is of relatively small diameter, such, for example, as 3" or 4", is fixedly clamped to the mounting disc 36, preferably at a level above that of the periphery of each member 42. The members 42 also define the lower boundary of the spaces 32 provided in the units 22. When air is introduced under pressure, by means to be described hereinafter, through the discharge opening 28 of each of the units 22, and passes through the ports 40 to the space 32 in each unit, the volume and pressure of such air is sufficient, particularl when the chair seat supported by the base 10 is not occupied, to cause the flexible member 42 of each unit to balloon downwardly a limited distance, as illustrated in exemplary manner in FIG. 5. The air is supplied continuously during movement of the chair, preferably at a steady rate and pressure, by the supply means described hereinafter.

Air delivered to spaces 32 tends to balloon members 42 downwardly and also continuously discharges through the pores of the unsealed portions of the flexible members 42 into the central space 60 below the central portion of each flexible member 42, which space extends from the point of tangency of the member 42 with the supporting floor surface 12, for example, inwardly toward the vertical central axis of each of the members 22. The pressure of air within spaces 32 against the inner surfaces of members 42 causes them to function as flexible seals defining the periphery of each central space 60. Some of the air in spaces 32 also is discharged through the member 42 substantially at the point of tangency thereof with the floor surface 12 so as to immediately engage said floor surface.

When air within the central space 60 of each unit reaches a pressure sufliciently high that the resultant force of pressure exerted on the particular area exceeds the weight of the chair base 10 and at least the chair seat 14 and back 16 supported thereby, the air confined within the central spaces 60 of the units 22 will discharge laterally between the periphery of the lower surface of member 42 and the supporting surface 12 against the sealing action described above, thereby creating a constantly discharging film of air therebetween upon which the chair base and any load supported thereby may glide horizontally readily and easily with respect to the supporting surface 12.

As can be appreciated especially from FIG. 5, where in the flexible porous member 42 is ballooned downwardly a greater distance then in the exemplary illustration shown in F IG. 6, there normally would be a substantial tendency for air within the interior spaces 32 to escape radially outward through the downwardly and inwardly extending peripheral portions of the members 42 between the point of tangency thereof with the floor and these portions of said members which engage the ring 52, for example, if nothing were present to prevent it. According to this invention, however, in order that no such useless and wasteful discharge of air shall occur through said aforementioned peripheral portion of any of the flexible, porous members 42 of the units 22, air-flow restricting means are provided which are specifically illustrated as an exemplary annular, flexible, impervious member 62.

The member 62 preferably is firmly afl'ixed to the inner surface of the peripheral portion of each member 42 and extends at least from the point of tangency of the member 42 with the supporting surface 12, outwardly radially so as to extend at least a short distance upwardly between the outer surface of the compressible ring 52 and the opposing portion of binding flange 44, as shown in exemplary manner in FIGS. and 6. The restricting member 62 may comprise, for example, a suitable thickness of flexible lacquer or other appropriate coating material which may be applied by spraying, or painting with a brush upon the inner surface of member 42 in the area described above so as to be firmly aflixed' to such inner surface of member 42. The coating is sufficiently thick to be impervious and thereby block or obstruct any passage of air from the space 32 through the peripheral portion of member 42 which is covered by the coating comprising said restricting member 62.

Air, under pressure, is generated and delivered to each of the discharge units 22 by mechanism preferably carried by the chair base and supported, for example, by the base plate 20. In FIGS. 3 and 4, it will be seen that an electric motor 64 is supported by an appropriate vertical pedestal member 66 and is for purposes of raising and lowering an upper support plate 68 to which the chair seat 14 is connected for support thereby. An appropriate flexible bellows 70 extends between the plate 68 and the upper portion of a shroud or cover 72, and encloses the mechanism illustrated in detail in FIGS. 3 and 4.

A supporting bracket plate 74 is connected by a plurality of shock-absorbing mounts 76 to base plate and supports a manifold housing 78 which surrounds and contains a blower-type air compressor of suitable capacity which is directly aflixed to the lower end of self-contained power means comprising, for example, an electric motor mounted within casing 80. The casing 80 also may include an appropriate filter through which incoming air is received for delivery to the blower within the manifold housing 78 for purposes of compressing the air taken in through the filter associated with the casing 80 for discharge through tangential scroll-like exhaust ports 82. One such port 82 is provided for each of the discharge units 22, as can best be seen from the plan view shown in FIG. 4.

Appropriate flexible conduits 84 are respectively clamped at one end to the terminal ends of the exhaust ports 82 and the opposite ends are connected to inlet collars 86, shown in FIGS. 5 and 6, which extend upwardly and preferably integrally from the center of a horizontal supporting flange 88 which, if desired, may be formed from sheet metal and extends across the discharge opening 28 in each corner of the base plate 20. Said supporting flange members 88 may be effectively connected to the base plate 20 by a suitable number of circumferentially spaced screws 90. Securing means such as hose clamps 92 effectively aflix the opposite ends of the conduits 84 respectively to the exhaust port members 82 and the inlet collars 86. Such conduits may be of the so-called radiator hose type and are fully capable of sustaining the air pressures transmitted therethrough.

As has been referred to above, the mechanism shown in FIGS. 3 and 4, by means of which the chair seat 14 is elevated and air under pressure is generated and distributed to the interiors of the air-discharge units 22, preferably is enclosed within an esthetically pleasing shroud or cover 72. If desired, said cover may be formed from several cooperating members 94 and 96, the same meeting along a central median line 98 for purposes of facilitating the mounting of the cover 72 upon the base plate 20 and removing it therefrom, especially for purposes of servicing the equipment which is normally obscured from view by the cover. Extending outwardly from at least certain portions of the lower edges of the members of cover 72 are flange portions 100 which support a plurality of suitable control switches 102.

By an appropriate circuit, not shown in detail but of conventional nature, said switches are connected to the several electric motors contained within the cover 72, respectively for purposes of raising and lowering the chair seat 14 and initiating operation of the blower motor for purposes of generating air under pressure to form an air film beneath each of the discharge units 22. In the preferred arrangement of said base and seat, incidentally, it is not intended that relative rotation between the base and seat shall occur about such vertical axis in order to permit the manipulation of the chain seat or back to guide the base while it is supported upon such air film. Further, only a light urging by the foot of the operator against one side surface of the flange portions of the base is all that normally is needed to gently and effectively cause the chair base and any load, such as a patient or patron supported thereby, to be moved horizontally or rotated about a vertical axis.

At the conclusion of such movement, it is only necessary to operate the appropriate control switch 102 for the blower motor in order to stop the blower which meanwhile has been operating continuously to effect desired air-guiding of the chair base. As soon as the motor switch is opened to stop the same, the chair base immediately settles onto the supporting surface 12 for firm support thereon by gravity. Similarly, the switches 102 which control the elevation or lowering of the seat with respect to the chair base are operated to effect such movements, but said switches preferably are of the type which must be held closed as long as operation is desired.

A duplicate set of somewhat remote control switches also may be provided, if desired, and mounted anywhere convenient, such as on the chair back 16. Further, it will be seen that by providing duplicate control means such as the switches 102 respectively at opposite sides of the chair base 10, as shown in FIG. 2, an operator, such as a dentist, readily can control the operation of the various functions of the chair base and seat thereon from either side of the base, as best suits his convenience.

By way of example only, and without limitation thereto, the units 22 illustrated in the drawings are each approximately 15 in diameter. Air is developed in the manifold 78 at approximately 2.5 lbs. per square inch. This system will readily sustain a maximum load of about 750 lbs., including the chair and occupant when air at the foregoing pressure range is discharged through the porous discharge members having the approximate porosity set forth hereinabove. The annular flow-restricting coatings 62, under such circumstances, will be between 2" and 2 /2 wide from the outer periphery inwardly and determine the effective discharge area of each unit 22.

One of the principal features with which the present invention is concerned comprises self-leveling of the base 10 with respect to the normally horizontal supporting surface such as a floor 12. It readily can be appreciated that if additional equipment is connected to the chair base 10 for support thereby and movement therewith as the same is either rotated about a vertical axis or moved horizontally over the supporting surface 12, or both, eccentric loading frequently results. By way of example, a horizontally extending bracket, not shown, may be connected to the upper support plate 68 which projects slightly above the top of cover 72, as shown in FIG. 1, immediately below the chair seat 14. The outer end of such bracket arm will extend beyond the corresponding side of chair seat 14, for example, and a vertical post member will project upwardly from the outer end of said horizontal bracket arm for purposes of supporting an ap propriate light or any other desired item of equipment at the upper end of said post. Under such circumstances, an eccentric load will be imposed upon the chair base 10.

Another example of eccentric loading may arise from the fact that a patient or patron is disposed within the chair seat 14 in an off-center position, so that the chair seat and base are located eccentrially either more to one side than the other, or more toward the front than the tear, or vice versa. Any of these situations imposes an eccentric loading upon the base 10 and, correspondingly,

such eccentric loading is transferred directly to one Or more of the air discharge units 22.

When an eccentric loading of the chair seat and base results in the load being heavier upon one of the discharge units 22 than the other, or upon several of them more than the third, there is a tendency to deflate the bottom air-discharge member 42 of that particular unit or units, which results in increased flattening of the same with respect to the periphery of the mounting plate 24 of that unit. Under this condition, the discharge member 42 of the more heavily loaded unit or units assumes the position illustrated in exemplary manner in FIG. 6. Under such circumstances, it will be seen that the outermost point of tengency of discharge member 42 with respect to the supporting surface 12 is substantially closer to the outer periphery of the unit 22 than when the unit is less heavily loaded, as exemplified by the illustration shown in FIG. 5, wherein it has been assumed, for example, that the chair seat 14 is unoccupied.

By flattening the lowermost portion of the discharge member 42 in accordance with the illustration shown in FIG. 6, as when one of several of said units are more heavily loaded than the others, it will be seen that a substantially increased overall flattened area of the member 42 results and, correspondingly, the area of the air film produced between such flattened portion of the member 42 and the supporting surface 12 is substantially greater than under the circumstances illustrated in FIG. 5. Also, the sealing effect of such flattened portion is increased under such circumstances. As a result, the increased sealing force produces a greater pressure in space 60 which, when it escapes between member 42 and floor surface 12, produces a greater sustaining force under the circumstances illustrated in exemplary manner in FIG. 6 than under the circumstances shown in FIG. 5. This result offsets or counteracts the heavier loading of one or more of the units 22 and thereby prevents the possibility of the outer edge of said one or more heavier loaded units from frictionally engaging the supporting surface 12, for example, which condition is somewhat similar to attempting to dig into the supporting surface, so to speak, and thereby impede horizontal movement of the chair base over the supporting surface.

The addition of the annular flow-restricting means 62 to the inner surface of the air-discharge member 42 adjacent the periphery thereof results in utilizing the discharging air to its highest efliciency to produce a sustaining air film more effectively than if the flow-restricting member 62 were not used. By utilizing a flow-restricting means 62 in the form of a coating which is integrally aifixed to the porous air-discharge member 42, there appears to be a tendency for vibration of the porous member 42 to develop, resulting, under some circumstances, in an audible, high pitched noise to be generated by the air film as it escapes peripherally from the space between the lower surface of member 42 and the supporting surface 12.

It has further been found, however, that great minimizing or elimination of the vibration and fluttering, as well as the resulting high pitched noise, may be accomplished by roughening at least the portion of the lower surface of member 42 which normally defines the upper surface of the air film when the chair base is floating thereon for movement parallel to the supporting surface 12. Such roughening of the member 42 may be efiected quite simply, such as by using sandpaper or the like and rubbing it sufficiently upon the lower surface of member 42 to produce at least a limited amount of fuzz composed of relatively short projecting ends of filaments or fibers from which the member 42 is woven or otherwise formed. Said projecting ends comprise portions of filaments which are partially or completely severed as a result of such abrasion by said sandpaper or the like. Continuous use results in additional beneficial roughening of this same type.

Production of the supporting air film also is rendered highly eflicient, for example, by connecting the central portion of the member 42 to the mounting disc 36 which is disposed at a higher elevation and parallel to the lower surface of the peripheral portion of mounting plate 24 and especially the lower surface of the compressible ring 52. As a result of such arrangement, even when the chair base is at rest, whereby a major portion of the radially outermost area of each of the members 42 are disposed flatly in engagement with the supporting surface 12, there nevertheless will be a central space 60 of useful height. Thus, when commencing the generation of air under pressure by the blower or compressor within motor casing 80, air introduced into the shallow interior space 32 of each of the discharge units 22 initially will pass through the pores or other type of minute openings in member 42 which are located in that portion thereof extending between the clamped central portion thereof and the innermost point of tangency of the member 42 with the supporting surface 12. Such air is discharged immediately into the central space 60.

When the resultant force of pressure within space 60 which is exerted on the particular area of member 42 circumscribing said space exceeds the total weight exerted downwardly upon the base 10 by the occupant of the chair 14, any additional apparatus and equipment supported by the base, as well as the dead weight of the base 10 and chair 14, the air within said central spaces 60 of the discharge units 22 will force an escape passage between the lower surfaces of the flattened portions of the air discharge members 42 and the supporting surface 12 and thereby produces a sustaining air film. Such air film is capable of supporting the chair base and any load supported thereby, whereby it may be moved readily and easily in any lateral direction, or rotated about a vertical axis, if desired, with respect to the supporting surface 12.

It also is to be understood, in accordance with the principles of the invention, that the discharge units 22 may be made of different capacities with respect particularly to the radial dimension of the flow-restricting means 62 on the porous discharge member 42 of each of said units, as well as the overall diameters of members 42. By way of specific example, it will be seen from FIG. 2 in particular that the relatively straight, right-hand edge 104 of the base 10, as viewed in FIG. 2, is intended to be the front or forward edge of the base. Said forward edge actually extends between a pair of the discharge units 22 disposed adjacent opposite ends of the forward edge 104 beneath the flange portions of the shroud or cover 72 of the base. The opposite end 106 of the base 10, adjacent the left-hand side of the sheet as viewed in FIG. 2, is considered the rear or trailing end of the base.

Considering the foregoing description of the edge 104 and trailing end 106 of the base in relation to FIG. 3, it will be seen, correspondingly, that the forward edge 104 is adjacent the right-hand side of the sheet while the trailing edge 104 is adjacent the right-hand side of the sheet while the trailing end of the base 106 is adjacent the lefthand side and this arrangement, when oriented with respect to FIG. 4, results in the lower edge of the assembly shown in FIG. 4, considered when the sheet is positioned vertically, comprising the forward edge of the base while the uppermost unit 22 is considered to be adjacent the trailing end of the base.

In the actual loading of the base 10, as when a person of normal Weight is seated within the chair seat 14 and the chair is disposed substantially in the relative position shown in FIG. 1 with respect to the base, the patients legs normally will extend horizontally forwardly substantially beyond the front edge 104 of base 10. As a result, the center of gravity of the actual load which is sustained under these circumstances by the base 10 will be more or less across the line of centers of the two units 22 which respectively define opposite ends of the front edge 104 of the base. Such an arrangement tends to concentrate most of the load, therefore, upon the two forward units 22 which are in transverse alignment with each other, considered in relation to the fore and aft axis of the assembled base and chair, while the rearmost unit 22 is only lightly loaded in comparison with the forward unit.

As a result of the foregoing situation, there normally is a tendency for the discharge member 42 of the rearmost unit 22 barely to touch the supporting floor surface 12, for example, under the circumstances described above. This situation may be obviated, however, by increasing the radial dimension of the flow-restricting means 62 of the rearmost unit 22 from the periphery, inward, which results in the annular area of the member 42 of said rearmost unit which engages the supporting surface 12 to move vertically downward, or balloon, a greater extent than the discharge members 42 of the forwardmost units 22. This effectively causes the member 42 of the rearmost unit to engage the supporting surface 12 and, as it were, actively participate in the sustaining of the base upon an air film when moving horizontally with respect to the suporting surface, either in rotary movements about a vertical axis or linearly.

The aforementioned greater ballooning effect of the rearmost unit 22 may be enhanced by initially connecting the peripheral portion of the flexible discharge member 42 of said rearmost unit around the periphery of the mounting plate 24 of said unit in a less taut manner than that in which the discharge member 42 is connected to the peripheries of the mounting plates 24 of the forwardmost units 22. Notwithstanding the looser attachment or connection of the member 42 to the periphery of the mounting plate 24 of the rearmost unit, with the resulting somewhat greater ballooning effect produced when air is discharged to the interior of said unit, the aforementioned greater width of the flow-restricting band means 62 is sufficient to prevent any direct peripheral escape of air under pressure through the peripheral portion of the member 42 of said rearmost unit between the point of tangency of said peripheral portion with the supporting surface 12 and the peripheral edge of the member 42 where it is connected to the periphery of mounting plate 24.

When, for any reason, it becomes necessary to service any of the units 22, the same may be accomplished readily and quickly simply by removing the several members 94 and 96 of the cover 72 to fully expose all of the interior components normally enclosed by said cover and comprising all of the functional members of the base 10. By removing the several bolts which operably connect each unit 22 to one corner of the base plate 20, the entire unit is separated from the base plate and any servicing or replacement which may be necessary or desired may be performed quickly and under conditions which permit maximum convenience of access to any parts of said units. Further, the entire mechanism by which the chair seat is raised or lowered likewise is fully accessible, as well as all components of the air compressing and distributing members.

Particularly because of the ability of the air-discharge units 22 to compensate for excessive or eccentric loading of one or more with respect to the others, especially by causing the more heavily loaded units to be compressed, or flattened, so to speak, with respect to the supporting surface 12 and thereby develop a greater area of sustaining air film of higher pressure between the discharge member 42 of that unit and the supporting surface 12, as compared with other less heavily loaded units, maximum ease of gliding movement upon a film of air over the supporting surface 12 is provided regardless of any eccentric loading of the base and the means thereby.

I claim:

1. A self-leveling mobile supporting means for a chair seat comprising:

(a) a chair base normally in supported engagement with a floor surface,

(b) means carried by said chair base for supporting a chair seat,

(c) a plurality of porous pad-like air discharge means on the bottom of said base and supportingly connected thereto,

(d) said pad-like air discharge means each comprising a substantially circular disc-like horizontal supporting member connected to said base and having a flexible porous air-discharge member connected to the periphery of each supporting member adjacent the lower face thereof and extending radially inward therefrom,

(c) said discharge member on each supporting member being engageable with a floor surface when supporting said base stationarily upon said floor, and

(f) means to direct air under pressure to the inner surface of each discharge member to discharge air therethrough to form a film of air between the discharge member and floor for horizontal gliding movement relative to said floor, said air at least partially inflating the discharge member away from said supporting member and thereby effect a yieldable seal between said discharge member and the floor to control the discharge of said air film from the periphery of said pad-like air discharge means, in combination with;

(g) air-flow restricting means on said porous airdischarge members comprising a flexible and substantially impervious coating firmly aflixed to the inner surface of each air-discharge members by flowing said coating in liquid form onto the same to cause penetration of the pores thereof to render said coating integrally bonded therewith so as to be flexibly movable therewith under all conditions of use and extending radially inwardly from the periphery thereof substantially to the point of engagement of said discharge member with a floor surface when inflated, thereby preventing useless peripheral discharge of air through said air-discharge members,

(h) said air-discharge members when inflated and subjected to load pressure downward tending to flatten the inflated portion into parallelism with such floor surface and produce an air film of greater sustaining force between said flattened portion of said discharge member and floor than when less heavily loaded and thereby provide a sustaining air film adequate to support loads of different weights while moving upon air films relative to a floor.

2. The mobile supporting means according to claim 1 further including a ring-like member of yieldable material extending around the periphery of each disc-like supporting member and the outer peripheral portion of said impervious coating extending upwardly in sealing engagement with the outer peripheral surface of said ring-like member on each supporting member, and clamping means securing the perimeter of each air-flow restricting means to the periphery of each supporting member and thereby maintaining said sealing engagement between said impervious coating and ring-like member on each pad-like air discharge means.

3. The mobile supporting means according to claim 1 in which there are three of said pad-like air-discharge means spaced substantially evenly around the circumference of said chair base, two of said air-discharge means being arranged in side-by-side relationship across the normal front of said chair base and the third air-discharge means extending from the normal trailing end of said chair base, and said means carried by said chair base for supporting a chair seat being positioned relative to said base so that when a chair seat is connected thereto for support and is occupied by a person the center of gravity of the resulting load upon said base will be located substantially mid-way along a line extending horizontally between the centers of said air-discharge means positioned across the normal front of said chair base.

4. The method of making a porous pad-like air discharge unit adapted to be attached to a chair base to render the same mobile over a supporting surface such as a floor and comprising a substantially circular and rela tively flat supporting member arranged horizontally in use, means on said member to attach it to the bottom of a chair base, and a flexible porous air discharge member formed from textile fabric and positioned adjacent the lower face of said supporting member, said porous member being peripherally coextensive with said supporting member and extending radially inward therefrom for engagement with a supporting floor surface when supporting a chair base stationarily upon such floor, said method comprising the steps of forming an air-flow restricting means on said porous air discharge member by flowing onto the surface thereof to be disposed nearest said supporting member a coating band of liquid material extending radially inward from the periphery of said porous member and permitting said coating to penetrate the pores thereof sufiiciently to bond said coating thereto, drying said coating to form an impervious air barrier around said peripheral portion of said member, and connecting the periphery of said porous member sealably to the periphery of said supporting member and thereby provide said air-discharge unit with means to prevent peripheral discharge of air.

5. The method of making an air discharge unit according to claim 4 including the further step of roughening the surface of said porous air-discharge member which normally will be nearest a floor surface, thereby to break certain of the fibers of said textile fabric and produce a fuzzy surface past which a film of supporting air will pass when said pad-like air-discharge unit is functioning to support a chair base for movement over a floor surface and thereby prevent chatter and flutter of said porous air-discharge member incident to such passage of air past said fuzzy surface.

References Cited UNITED STATES PATENTS 3,243,004 3/1966 Mackie 180-124 3,347,330 10/1967 Heathe 180118 A. HARRY LEVY, Primary Examiner.

US. Cl. X.R. 180121 

